Hepatitis A Outbreak in France and Europe - Update as of September 11, 2017

Published on 26 September 2017

Since February 2017, several European countries have seen a significant increase in the number of hepatitis A cases, particularly among men who have sex with men (MSM); three "epidemic" strains of the hepatitis A virus are primarily responsible for this. Cases linked to this outbreak have been reported in many European countries (Austria, Belgium, Denmark, Finland, France, Germany, Greece, Ireland, Italy, the Netherlands, Norway, Portugal, Slovenia, Spain, Sweden, and the United Kingdom).

The situation in France

Hepatitis A is monitored in France through mandatory reporting and by the National Reference Center (CNR).

Epidemiological data

From January 1 to August 31, 2017, 2,060 cases of hepatitis A were reported: 66 in January, 90 in February, 158 in March, 195 in April, 310 in May, 354 in June, 472 in July, and 415 in August. The number of hepatitis A cases reported during the first 8 months of 2017 is already three times higher than the total number of cases reported in 2016 (693 cases).

This outbreak primarily affects men, who account for 1,639 (80%) of the 2,060 cases reported in 2017 (Figure 1).

Sexual orientation is not included in the information collected as part of the mandatory reporting system. However, clusters of cases among MSM are suggested when an increase in the male-to-female sex ratio is observed among reported cases and none of the classic risk factors are present (other cases or children in the social circle, work in a high-risk setting, travel outside mainland France, or consumption of seafood), or when sexual orientation is documented during investigations.

The analysis of the male-to-female sex ratio presented below focused on cases aged 18 to 55, the most affected age group, to avoid accounting for potential polyclonal reactions (a resurgence of hepatitis A-specific antibodies several years after a past infection), which are more common in those over 55.

The observed increase in the male-to-female sex ratio (4 in 2017 vs. 1 in 2016) and the results of initial investigations into clusters of cases strongly suggest that the MSM population is the most affected by this epidemic, in France as in other European countries.

The most affected regions are Île-de-France (468), Hauts-de-France (359), followed by Auvergne-Rhône-Alpes (317), Provence-Alpes-Côte d'Azur (237), Occitanie (152), and Nouvelle-Aquitaine (136) (Map).

Starting in January 2017, the male-to-female sex ratio among the 1,646 cases aged 18 to 55 increased (to around 8) and then decreased between May and June, remaining relatively stable (around 5) between July and August (Figure 2). By region, the sex ratio increased but to varying degrees. It is currently highest in the PACA (14) and Île-de-France (10) regions, followed by the Hauts-de-France and ARA regions at around 6, and finally around 4 for the Nouvelle-Aquitaine region.

Virological data

Between late 2016 and September 6, 2017, the CNR identified the presence in mainland France of three European "epidemic" strains circulating among MSM in many European countries. These strains are:

RIVM-HAV16090, known as "Nl Europride,"
VRD-521-2016, known as "UK travel to Spain,"
V16-25801, known as "Germany Munich/Berlin/Frankfurt."

During this period, the CNR identified 792 samples containing one of these three strains; 700 (88%) of these samples were from men, with an average age of 36. The CNR’s genotyping results were as follows: 454 (57%) of the strains were of the VRD-521-2016 type, 319 (40%) of the RIVM-HAV16090 type, and 19 (2%) of the V16-25801 type.

In summary

The hepatitis A outbreak is currently affecting all metropolitan regions, albeit to varying degrees, with significant transmission among MSM. A slight decrease in the number of cases among men was observed between July and August.

Since May 2017, a moderate increase in the number of cases among women has been observed, resulting in a decrease in the sex ratio. In fact, 12% of European strains were identified by the CNR in women. This increase could be linked to clusters of cases observed in the general population within family households, as well as following visits to restaurants after consuming food contaminated by a food handler with hepatitis A. Furthermore, a slight increase in the number of cases among those under 15 was observed between July and August.

These increases among women and those under 15 suggest a spread from the MSM community to the general population. Overall, the decrease in the number of cases among men and the spread to the general population will need to be confirmed in the coming months.